^^Meh, that's not the standout example. Bisharp rose from UU to OU. Mandibuzz, on the other hand rose all the way from NU, without getting any new moves or whatnot. Buffed Knock Off. Buffed Defog. Buffed Overcoat. Buffed Whirlwind, even (it now penetrates Protect). Stealth Rock less dominant. Not having to care about sun- and rain-boosted attacks (especially Thunder) any more. Sticky Web immunity. Excellent response to new threats such as Aegislash. I could go on.
(Oh, I may be in the minority here but IMO Mandibuzz was quite an unhealthy presence in Gen V NU - it was just too hard for stall teams to kill. It's just that Jynx and Scolipede were worse and so it didn't get noticed.)